Bump structure with annular support and manufacturing method thereof

ABSTRACT

A bump structure with an annular support suitable for being disposed on a substrate is provided. The substrate has at least one pad and a passivation layer that has at least one opening exposing a portion of the pad. The bump structure with the annular support includes an under ball metal (UBM) layer, a bump, and an annular support. The UBM layer is disposed on the passivation layer and covers the pad exposed by the passivation layer. The bump is disposed on the UBM layer over the pad, and a diameter of a lower surface of the bump is less than the diameter of an upper surface thereof. The annular support surrounds and contacts the bump, and a material of the annular support is photoresist. An under cut effect is not apt to happen on the bump structure.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of P.R.C. applicationserial no. 200710004497.4, filed Jan. 16, 2007. All disclosure of theP.R.C. application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a bump structure and a manufacturingmethod thereof, and more particularly to a bump structure with anannular support and a manufacturing method thereof.

2. Description of Related Art

Flip chip interconnect technology is a packaging technique forconnecting a die to a circuit board, which is mainly conducted byforming a plurality of bumps on respective pads of the die, flipping thedie over, and connecting the pads of the die to terminals on the circuitboard via the bumps, such that the die is electrically connected to thecircuit board through the bumps. In general, the bumps are of varioustypes such as solder bumps, gold bumps, copper bumps, conductive polymerbumps, polymer bumps, and so forth.

FIG. 1A is a cross-sectional view of a conventional gold bump, whileFIG. 1B is a top view of the conventional gold bump. Referring to FIGS.1A and 1B, a conventional gold bump structure is adapted to be disposedon a die 110 on which a plurality of aluminum pads 120 (only onealuminum pad shown in FIGS. 1A and 1B) and a passivation layer 130 areformed. The passivation layer 130 has a plurality of openings 130 aexposing a portion of each of the aluminum pads 120, respectively. Inaddition, the conventional gold bump structure includes an under ballmetal (UBM) layer 140 and a gold bump 150. The UBM layer 140 is disposedwithin the opening 130 a and covers a portion of the passivation layer130. The gold bump 150 is disposed on the UBM layer 140. The gold bump150 covers the UBM layer 140 over the portion of the passivation layer130, resulting in formation of an annular protrusion 150 a of the goldbump 150. This is called a wall effect. The annular protrusion 150 a maypose an impact on the bonding strength between the gold bump 150 andother carriers (not shown). Moreover, the UBM layer 140 is disposedright below the gold bump 150. Accordingly, as cracks are formed betweenthe UBM layer 140 and the gold bump 150, or, between the UBM layer 140and the passivation layer 130, an under cut effect on the conventionalgold bump structure can often be expected.

SUMMARY OF THE INVENTION

The present invention provides a bump structure with an annular supportto reduce an under cut effect.

The present invention provides a manufacturing method of a bumpstructure with an annular support to sufficiently avoid a wall effect.

The present invention provides a bump structure with an annular supportsuitable for being disposed on a substrate. The substrate includes atleast a pad and a passivation layer which has at least an openingexposing a portion of the pad. The bump structure with the annularsupport includes an under ball metal (UBM) layer, a bump, and an annularsupport. The UBM layer is disposed on the passivation layer and coversthe pad exposed by the passivation layer. The bump is disposed on theUBM layer over the pad, and a diameter of a lower surface of the bump isless than the diameter of an upper surface thereof. The annular supportsurrounds and contacts the bump, and a material of the annular supportis photoresist.

According to one embodiment of the present invention, the bump includesa head and a neck connecting the head to the UBM layer, and a diameterof the head exceeds the diameter of the neck.

According to one embodiment of the present invention, the diameter ofthe bump increases from the lower surface of the bump to the uppersurface thereof.

According to one embodiment of the present invention, a diameter of theannular support is less than or equal to the diameter of the uppersurface of the bump.

According to one embodiment of the present invention, the diameter ofthe annular support decreases from the upper surface of the bump to thelower surface thereof.

According to one embodiment of the present invention, the bump includesa gold bump.

The present invention provides a manufacturing method of a bumpstructure with an annular support. The manufacturing method includes thefollowing steps. First, a substrate including a plurality of pads and apassivation layer is provided. The passivation has a plurality of firstopenings, and each of the first openings exposes a portion of the pad.Next, an UBM material layer is formed on the passivation layer so as tocover the passivation layer and the pads exposed by the passivationlayer. Then, a patterned photoresist layer is formed on the UBM materiallayer. The patterned photoresist layer has a plurality of secondopenings respectively exposing the UBM material layer over the pads. Adiameter of each of the second openings located on a lower surface ofthe patterned photoresist layer is less than the diameter of each of thesecond openings located on an upper surface of the patterned photoresistlayer. Thereafter, a plurality of bumps is formed in the secondopenings. Afterwards, a portion of the patterned photoresist layer isremoved to form an annular support at a periphery of each of the bumps.The UBM material layer is then patterned with use of the annularsupports and the bumps as masks, such that a plurality of UBM layers isformed.

According to one embodiment of the present invention, the method offorming the patterned photoresist layer includes using a photomask toincrease the diameter of each of the second openings from the lowersurface of the patterned photoresist layer to the upper surface thereof.

According to one embodiment of the present invention, the photomaskincludes a half tone mask.

According to one embodiment of the present invention, the method offorming the patterned photoresist layer includes using a half tone maskfor enabling each of the second openings to have a head and a neck. Theneck connects the head to the UBM material layer, and a diameter of thehead exceeds the diameter of the neck.

According to one embodiment of the present invention, the method ofremoving the portion of the patterned photoresist layer includesperforming a dry etching process with use of the bumps as the masks.

According to one embodiment of the present invention, the dry etchingprocess includes a plasma etching process.

According to one embodiment of the present invention, the method ofremoving the portion of the patterned photoresist layer includes thefollowing steps. First, an exposure process is performed on thepatterned photoresist layer with use of the bumps as the masks. Next, adeveloping process is performed on the exposed patterned photoresistlayer so as to remove the portion of the patterned photoresist layer.

In view of the foregoing, the bump structure of the present inventionhas the annular support, and thus the under cut effect is not apt tohappen. In addition, the bumps are formed within the opening of thepassivation layer according to the present invention. Hence, the bumpstructure of the present invention has a planar upper surface.

In order to make the aforementioned and other objects, features andadvantages of the present invention more comprehensible, severalembodiments accompanied with figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view of a conventional gold bump.

FIG. 1B is a top view of the conventional gold bump.

FIGS. 2A through 2D are schematic views depicting a manufacturing methodof a bump structure with an annular support according to a firstembodiment of the present invention.

FIGS. 3A through 3D are schematic views depicting a manufacturing methodof a bump structure with an annular support according to a secondembodiment of the present invention.

DESCRIPTION OF EMBODIMENTS First Embodiment

FIGS. 2A through 2D are schematic views depicting a manufacturing methodof a bump structure with an annular support according to a firstembodiment of the present invention. Referring to FIG. 2A first, themanufacturing method of the bump structure with the annular supportaccording to the present embodiment includes the following steps. First,a substrate 210 including a plurality of pads 220 and a passivationlayer 230 is provided. The passivation layer 230 has a plurality offirst openings 230 a, and each of the first openings 230 a exposes aportion of the pad 220. To better illustrate the present embodiment, itshould be noted that only one of the first openings 230 a and one of thepads 220 are shown in the figures. In addition, the substrate 210 may bea wafer or any other carrier, and a material of the pad 220 may bealuminum, copper, or any other metal.

Referring to FIG. 2A again, an under ball metal (UBM) material layer 310is then formed on the passivation layer 230 so as to cover thepassivation layer 230 and the pad 220 exposed by the passivation layer230. Moreover, the method of forming the UBM material layer 310 includesimplementing a sputtering process, a physical vapor deposition (PVD)process, or a chemical vapor deposition (CVD) process.

Then, a patterned photoresist layer 320 is formed on the UBM materiallayer 310. The patterned photoresist layer 320 has a plurality of secondopenings 322 respectively exposing the UBM material layer 310 over thepads 220. A diameter of each of the second openings 322 located on alower surface of the patterned photoresist layer 320 is less than thediameter of each of the second openings 322 located on an upper surfaceof the patterned photoresist layer 320. Further, the method of formingthe patterned photoresist layer 320 includes using a photomask (notshown). For example, the photomask is a half tone mask which is adoptedto enable each of the second openings 322 to have a head 322 a and aneck 322 b. The neck 322 b connects the head 322 a to the UBM materiallayer 310, and a diameter of the head 322 a exceeds the diameter of theneck 322 b. To avoid a wall effect, the diameter of the neck 322 b maybe less than the diameter of the first opening 230 a.

Referring to FIG. 2B, a plurality of bumps 330 is formed in the secondopenings 322. In other words, the bumps 330 are formed on the UBMmaterial layer 310 over the pads 220 exposed by the passivation layer230. A diameter of a lower surface of the bump 330 is less than thediameter of an upper surface of the bump 330. In the present embodiment,each of the bumps 330 includes a head 332 and a neck 334 connecting thehead 332 to the UBM material layer 310. The diameter of the head 332exceeds the diameter of the neck 334, while the diameter of the neck 334is less than the diameter of the first opening 230 a. Additionally, theupper surface of the head 332 is planar. The method of forming the bumps330 may include performing an electroplating process, and the bumps 330are, for example, gold bumps or copper bumps.

Referring to FIG. 2C, a portion of the patterned photoresist layer 320is removed to form an annular support at a periphery of each of thebumps 330. According to different methods of removing the portion of thepatterned photoresist layer 320, an annular support 324 a or anotherannular support 324 b may be formed. In addition, the method of removingthe portion of the patterned photoresist layer 320 may includeperforming a dry etching process with use of the bumps 330 as masks. Thedry etching process is, for example, a plasma etching process. If theplasma etching process is performed to remove the portion of thepatterned photoresist layer 320, the annular support 324 a with avertical sidewall may be formed. That is to say, a diameter of theannular support 324 a is less than and equal to the diameter of theupper surface of the bump 330.

However, it is known to people skilled in the art that other methods ofremoving the portion of the patterned photoresist layer 320 areavailable. For example, the method of removing the portion of thepatterned photoresist layer 320 may include the following steps. First,an exposure process is performed on the patterned photoresist layer 320with use of the bumps 330 as the masks. Next, a developing process isperformed on the exposed patterned photoresist layer 320 so as to removethe portion of the patterned photoresist layer 320. If the exposureprocess and the developing process are carried out once again forremoving the portion of the patterned photoresist layer 320, the annularsupport 324 b with a recess portion may be formed; namely, the diameterof the annular support 324 b decreases from the upper surface of thebump 330 to the lower surface thereof.

Referring to FIG. 2D, the UBM material layer 310 is then patterned withuse of the annular support 324 a (or 324 b) and the bumps 330 as themasks, such that a plurality of UBM layers 312 is formed. Up to present,the manufacturing process of the bump structure with the annular supportaccording to the present embodiment is basically completed. Moreover, asthe substrate 210 denotes a wafer, a cutting process may also beperformed on the substrate 210 after the completion of saidmanufacturing process, such that a plurality of die structures (notshown) is formed. A description of the detailed bump structure with theannular support is provided hereinafter.

Referring to FIG. 2D again, the bump structure with the annular supportin the present embodiment is adapted to be disposed on a substrate 210having at least a pad 220 and a passivation layer 230. The passivationlayer 230 has a first opening 230 a exposing a portion of the pad 220.The substrate 210 may be a die or a wafer. The bump structure with theannular support includes an UBM layer 312, a bump 330, and an annularsupport 324 a (or 324 b). The UBM layer 312 is disposed on thepassivation layer 230 and covers the pad 220 exposed by the passivationlayer 230.

The bump 330 is disposed on the UBM layer 312 over the pad 220, and adiameter of a lower surface of the bump 330 is less than the diameter ofan upper surface thereof. According to one embodiment of the presentinvention, the bump 330 includes a head 332 and a neck 334 connectingthe head 332 to the UBM layer 312, and a diameter of the head 332exceeds the diameter of the neck 334. To avoid a wall effect, thediameter of the neck 334 may be less than the diameter of the firstopening 230 a. Additionally, a material of the bump 330 is, for example,gold or copper. The annular support 324 a (or 324 b) surrounds andcontacts the bump 330, and a material of the annular support 324 a (or324 b) is photoresist.

The bump structure of the present embodiment is equipped with theannular support 324 a (or 324 b) to protect the neck 334 of the bump330, and thus an under cut effect on said bump structure is not apt tohappen. Moreover, the neck 334 of the bump 330 is formed within thefirst opening 230 a, and the diameter of the neck 334 is less than thediameter of the first opening 230 a. Accordingly, the bump structurewith the annular support has a planar upper surface so as to avoid thewall effect in the related art.

Second Embodiment

The same or similar reference numbers used in a second embodiment and inthe first embodiment represent the same or the like elements, and thesecond embodiment is approximately identical to the first embodiment.The difference between the two embodiments is described hereafter, andthe similarities therebetween are omitted.

The difference between the bump structure with the annular supportprovided in the present embodiment and the same provided in the firstembodiment lies in that the bump in the present embodiment is equippedwith neither a head nor a neck. Instead, a diameter of the bump in thepresent embodiment increases from a lower surface of the bump to anupper surface thereof.

FIGS. 3A through 3D are schematic views depicting a manufacturing methodof a bump structure with an annular support according to a secondembodiment of the present invention. Referring to FIG. 2A first, themanufacturing method of the bump structure with the annular supportaccording to the present embodiment includes the following steps. First,a substrate 210 is provided. The description of the substrate 210 isclearly disclosed in the first embodiment, and thus no furtherexplanation is provided herein.

Next, referring to FIG. 3A, an UBM material layer 410 is formed on apassivation layer 230 so as to cover the passivation layer 230 and a pad220 exposed by the passivation layer 230. In addition, the method offorming the UBM material layer 410 may include performing a sputteringprocess or other PVD processes.

Then, a patterned photoresist layer 420 is formed on the UBM materiallayer 410. The patterned photoresist layer 420 has a plurality of secondopenings 422 respectively exposing the UBM material layer 410 over thepads 220. A diameter of each of the second openings 422 located on alower surface of the patterned photoresist layer 420 is less than thediameter of each of the second openings 422 located on an upper surfaceof the patterned photoresist layer 420. In the present embodiment, thediameter of the second opening 422 increases from the lower surface tothe upper surface, resulting in that the diameter of the lower surfaceof the second opening 422 is less than that of the first opening 230 a.Besides, the method of forming the patterned photoresist layer 420 mayinclude employing a half tone mask. However, the method of forming thepatterned photoresist layer 420 is not limited to this. It is known topeople skilled in the art that other methods of forming the patternedphotoresist layer 420 are available. For example, a depth of focus of anincident light may be changed to form the second openings 422 on thepatterned photoresist layer 420.

Referring to FIG. 3B, a plurality of bumps 430 is formed in the secondopenings 422. In other words, the bumps 430 are formed on the UBMmaterial layer 410 over the pads 220 exposed by the passivation layer230. A diameter of a lower surface of the bump 430 is less than thediameter of an upper surface of the bump 430. According to the presentembodiment, the diameter of each of the bumps 430 increases from thelower surface of the bump 430 to the upper surface thereof. The diameterof the lower surface of the bump 430 is less than the diameter of thefirst opening 230 a, and therefore the upper surface of the bump 430 isplanar. Moreover, the method of forming the bumps 430 includesperforming an electroplating process, and the bumps 430 are, forexample, gold bumps or copper bumps.

Referring to FIG. 3C, a portion of the patterned photoresist layer 420is removed to form an annular support 424 a (or 424 b) at a periphery ofeach of the bumps 430. The method of removing the portion of thepatterned photoresist layer 420 is referred to as the method of removingthe portion of the patterned photoresist layer 320 according to thefirst embodiment. In brief, if a plasma etching process is performed toremove the portion of the patterned photoresist layer 420, the annularsupport 424 a with a vertical sidewall may be formed. That is to say, adiameter of the annular support 424 a is less than and equal to thediameter of the upper surface of the bump 430. On the other hand, if anexposure process and a developing process are carried out twice forremoving the portion of the patterned photoresist layer 420, the annularsupport 424 b with a recess portion may be formed; namely, the diameterof the annular support 424 b decreases from the upper surface of thebump 430 to the lower surface thereof.

Referring to FIG. 3D, the UBM material layer 410 is then patterned withuse of the annular support 424 a (or 424 b) and the bumps 430 as masks,such that a plurality of UBM layers 412 is formed. Up to present, themanufacturing process of the bump structure with the annular supportaccording to the present embodiment is basically completed. Moreover, asthe substrate 210 is a wafer, a cutting process may also be performed onthe substrate 210, such that a plurality of die structures (not shown)is formed. Here, the difference between the bump structure with theannular support provided in the present embodiment and the bumpstructure with the annular support provided in the first embodiment willbe demonstrated hereinafter.

Referring to FIGS. 2D and 3D, the difference between the bump structurewith the annular support provided in the present embodiment and the bumpstructure with the annular support provided in the first embodiment liesin that the bump 430 in the present embodiment is not equipped with ahead 332 and a neck 334 as is the bump 330. The diameter of the bump 430increases from the lower surface of the bump 430 to the upper surfacethereof, and an inner diameter of the annular support 424 a (or 424 b)also increases from the lower surface of the annular support 424 a (or424 b) to the upper surface thereof.

Based on above, the present invention at least has the followingadvantages:

1. The bump structure of the present invention has the annular support,and thus the under cut effect on said bump structure is not apt tohappen.

2. The bumps are formed within the openings of the passivation layeraccording to the present invention. Hence, the bump structure of thepresent invention has the planar upper surface.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. A bump structure with an annular support suitablefor being disposed on a substrate comprising at least a pad and apassivation layer, wherein the passivation layer comprises at least anopening exposing a portion of the pad, the bump structure comprising: anunder ball metal (IBM) layer which is disposed on the passivation layerand covers the portion of the pad exposed by the passivation layer; abump disposed on the UBM layer over the pad, a diameter of a lowersurface of the bump being less than the diameter of an upper surface ofthe bump; and an annular support surrounding and contacting the bump, amaterial of the annular support being photoresist.
 2. The bump structureof claim 1, wherein the bump comprises a head and a neck connecting thehead to the UBM layer, and a diameter of the head exceeds the diameterof the neck.
 3. The bump structure of claim 1, wherein the diameter ofthe bump increases from the lower surface of the bump to the uppersurface thereof.
 4. The bump structure of claim 1, wherein a diameter ofthe annular support is less than or equal to the diameter of the uppersurface of the bump.
 5. The bump structure of claim 4, wherein thediameter of the annular support decreases from the upper surface of thebump to the lower surface thereof.
 6. The bump structure of claim 1,wherein the bump comprises a gold bump.
 7. A manufacturing method of abump structure with an annular support, comprising: providing asubstrate having a plurality of pads and a passivation layer having aplurality of first openings, each of the first openings exposing aportion of the pad; forming an under ball metal (UBM) material layer onthe passivation layer so as to cover the passivation layer and the padsexposed by the passivation layer; forming a patterned photoresist layeron the UBM material layer, wherein the patterned photoresist layer has aplurality of second openings respectively exposing the UBM materiallayer over the pads, and a diameter of each of the second openingslocated on a lower surface of the patterned photoresist layer is lessthan the diameter of each of the second openings located on an uppersurface of the patterned photoresist layer; forming a plurality of bumpsin the second openings; removing a portion of the patterned photoresistlayer so as to form an annular support at a periphery of each of thebumps; and patterning the UBM material layer with use of the annularsupports and the bumps as masks, such that a plurality of UBM layers isformed.
 8. The manufacturing method of claim 7, wherein the method offorming the patterned photoresist layer comprises using a photomask toincrease the diameter of each of the second openings from the lowersurface of the patterned photoresist layer to the upper surface thereof.9. The manufacturing method of claim 8, wherein the photomask comprisesa half tone mask.
 10. The manufacturing method of claim 7, wherein themethod of forming the patterned photoresist layer comprises using a halftone mask for enabling each of the second openings to have a head and aneck connecting the head to the UBM material layer, a diameter of thehead exceeding the diameter of the neck.
 11. The manufacturing method ofclaim 7, wherein the method of removing the portion of the patternedphotoresist layer comprises performing a dry etching process with use ofthe bumps as the masks.
 12. The manufacturing method of claim 11,wherein the dry etching process comprises a plasma etching process. 13.The manufacturing method of claim 7, wherein the method of removing theportion of the patterned photoresist layer comprises: performing anexposure process on the patterned photoresist layer with use of thebumps as the masks; and performing a developing process on the exposedpatterned photoresist layer so as to remove the portion of the patternedphotoresist layer.